If you are going to Ireland to do genealogical work, you absolutely must read this. Note the date: 1901, age of the automobile, nearly the age of flight. Yet this establishes that among the ordinary Irish (your probable targets of research), fathers and sons, siblings, even one man at different times, would use differnet surnames. If you can't turn up the father of Charles Murphy, it may be because he's in records as Liam Tiler. Surnames had not yet been frozen into family names in their minds, and they thought nothing of using whichever one they pleased, a level of chaos that you have to go back to the 1400s in England to find.

Good luck, and be glad this was here to read!